Numerous types of bulkheads have been used to divide a body of water from land, i.e., to support the earth and to maintain a water-earth boundary. FIG. 1 illustrates one type of prior art bulkhead 10A which divides a body of water 11A from land 13A. Bulkhead 10 includes generally vertical facing or piling 12A which is formed of either concrete, steel or wood. The bottom edge of piling 12A is driven or inserted into the channel bottom. In situations where the water is relatively shallow and the wall is very short, driving the bottom edge of the piling into the channel bottom sufficiently supports the bulkhead to retain or hold back the ground from the water. However, if the water is deep and the bulkhead is high, additional support for the bulkhead is required. FIG. 1 illustrates a typical technique for providing the additional support wherein a tie rod 14A is connected at one of its ends to piling 12A through a wale 21A and at its other end to a dead man 16A. Support piles 18A may also be attached to dead man 16A to provide further support.
Another technique for providing additional support to a bulkhead is through the use of tiebacks inserted at angles below horizontal through a wall and into the adjacent ground. The tiebacks are fixed into the ground, post-tensioned, and secured to the bulkhead. In each of these cases, the bulkhead is designed to provide a vertical span between the tie rods and the soil below the water, while the wale is designed to provide a horizontal span between the tie rods or tiebacks. Thus, the strength exhibited by the bulkhead is limited by its design and the depth of the water.
FIG. 2 illustrates a typical prior art technique for rehabilitating bulkhead 10A. Rehabilitation of a bulkhead 10A is required because of a failure or break 15A in tie rod 14A. However, rehabilitation of a bulkhead may be necessitated by other reasons including deterioration or corrosion in the bulkhead facing, raising the earth adjacent to the bulkhead, or a deepening of the channel bottom. In the illustrated rehabilitation technique, a new bulkhead 20A is installed a predetermined distance in front of, i.e., to the water-side, original bulkhead 10A. Bulkhead 20A includes piling 22A which is driven or inserted into the channel bottom to provide the toe for the lower end support of bulkhead 20A. Support at the upper end of bulkhead 20A is provided by a tieback 24A which is attached to a wale adjacent to the upper end of pile 22A. Tieback 24A extends toward the land-side at an angle below the horizontal through the original bulkhead 10A and into the ground behind bulkhead 10A.
In this technique the sequence of installation requires backfilling after installing the tiebacks. Since the tiebacks are installed prior to backfilling, the expensive technique of working from a barge or trestle may be required. Also, backfilling over and around a tendon or tiebacks may result in flexure and tensioning of the tieback, thereby increasing the chance of tieback failure. Another disadvantage of this rehabilitation technique is that temporary support of the new bulkhead during testing of the tiebacks is usually required. This technique in contrast to the bulkhead rehabilitaion technique disclosed herein, derives no residual value from the existing bulkhead since the existing bulkhead is not incorporated into the new structural system.
Another bulkhead rehabilitation technique is disclosed in U.S. Pat. No. 4,480,945 issued to Harry Schnabel, Jr. on Nov. 6, 1984, the U.S. Pat. No. 4,480,945 discloses a technique where tiebacks are installed in the bulkhead being rehabilitated. A sufficient number of tiebacks are installed so that all the additional required support is provided by the tiebacks. While the technique disclosed in the U.S. Pat. No. 4,480,945 is an advance over the previously discussed bulkhead rehabilitation technique since it is substantially less expensive and utilizes the existing bulkhead, in some situations a new bulkhead facing may be desired or the original bulkhead may be so severely deteriorated that tieback rehabilitaion alone would be insufficient.